Jach Feng 在 2023年1月22日 星期日上午11:11:22 [UTC+8] 的信中寫道：
> Fail on command line,
>
> e:\Works\Python>py infix2postfix.py "-4^2+5.3*abs(-2-1)/2"
> usage: infix2postfix.py [-h] [infix]
> infix2postfix.py: error: unrecognized arguments: -4^2+5.3*abs(-2-1)/2
>
> Also fail in REPL,
>
> e:\Works\Python>py
> Python 3.8.8 (tags/v3.8.8:024d805, Feb 19 2021, 13:08:11) [MSC v.1928 32 bit
> (Intel)] on win32
> Type "help", "copyright", "credits" or "license" for more information.
> >>> import argparse
> >>> parser = argparse.ArgumentParser(description='Convert infix notation to
> >>> postfix')
> >>> parser.parse_args("-4^2+5.3*abs(-2-1)/2")
> usage: [-h]
> : error: unrecognized arguments: - 4 ^ 2 + 5 . 3 * a b s ( - 2 - 1 ) / 2
>
> Just can't figure out where is wrong!?
>
> --Jach
OK, I take a quick try to use argv directly. I write the code in a way even get
rid of the -h option.
import sys
if len(sys.argv) == 1:
....infix = " "
....print("Usage: a math equation must follow!")
else:
....infix = "".join(sys.argv[1:])
Simple enough, right? But unfortunately it didn't survive. The ^ symbol was
lost!
e:\Works\Python>py infix2postfix.py
Usage: a math equation must follow!
e:\Works\Python>py infix2postfix.py -4^2 +5.3 * abs(-2-1)/2
-42 5.3 -2 1 - abs * 2 / +
Hmm...
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